Sorry for hijacking this thread but I am having same problem in my WPF Prism application.
The application has main menu that resides in its own module as usercontrol:
The MenuItems for Account Management subMenu are inserted dynamically when Account Management Module is loaded.
Here is a code for MenuItem Usercontrol:
When I am clicking on Account Requirements MenuItem the View is being displayed but Account Management Dropdown menu is stays open until I click somewhere outside of it .
Clicking on File->Exit works as expected - event fired and menu closed automatically.